FORM-2
THE PATENTS ACT, 19 70
( 39 of 1970 )

SPECIFICATION
S E C T ION 10

APPLICANT
BAJAJ AUTO LTD. an Indian Company, of Akurdi Pune 411 035, Maharashtra, India.
Invention and the manner in whichitls to be performed

This invention relates to I gear shifting system /Used in 2 or 3 wheeled vehicles having a ".handle bar steering control and hand operated gearshift control located on left hand side of the handle bar.
. These vehicles are provided with a gear shift control in conjunction with clutch control that is located on left hand side of the handle bar. This control is in the form of a twist grip provided with a clutch lever. In known vehicles, to shift gears, the twist grip is required to be rotated about its axis angularly, after depressing the clutch lever, till the desired-gear is engaged and then the clutch lever is progressively released. The twist grip is rotated in anti-clockwise direction, looking from the left hand side of the vehicle to shift gears in rt-Neutrai-2ncf-3rd-4th gear sequence after shifting from neutral to first in opposite direction. While to shift the gears through 4th-3rd-2nd-NeutraI-1st gear sequence, the twist grip is rotated in clockwise direction looking from the left hand side of the vehicle where one can discontinue shifting at neutral position. The sequence of shifting may vary depending upon vehicle model but one common feature is that the shifting takes place from a particular gear position to next higher or lower gear position and every time the angular position of the twist grip progressively increases or decreases while shifting gears. The gear shifting is achieved through two flexible gear control cables, one end of the flexible cable is connected to the pulley which is fixed to a tube which
' is press fitted to twist grip and the other end is connected to the gear shifter pulley, located in gear shifter housing. Once the twist grip is rotated and gear is selected, said two pulleys, in the process, change their initial positions to new ones and maintains their new positions till the rider desires the next gearshift. When the pulley of the gear shifter housing rotates, the gear shifter pin pushes the cross provided in main shaft to match the desired gear and rotational motion of the gear is transmitted to the main shaft on which the rear wheel is mounted. As main shaft rotates, the rear wheel also rotates and vehicle starts moving forward. The system explained above is very well known and does not need any further detailed explanation.
This type of gear shifting operation has certain difficulties as mentioned hereinbelow:
1) The angular position of twist grip and clutch control lever provided on the left hand side of the handle bar assembly is required to be changed as per the gear to be selected and it is required to be maintained in the same state, till next gear shift is

made. The left-hand fingers have to be kept on clutch lever, ready for next gearshift, which makes it troublesome for the driver to steer the vehicle.
2) The position explained in 1) above, makes it difficult for the driver to reach various other controls located on twist grip which are meant for switching headlamp, direction indicators, horn, etc.
3) While driving the vehicle in the fourth gear, the angular position of the clutch lever is at extremity and it is cumbersome to shift the gear to lower gears.
4) While driving the vehicle, if the rider twists the twist grip further after the selection of a particular gear, unintentionally, the next higher / lower gear may be engaged i.e. consecutive sequence of gear shifting may not be achieved.
In order to avoid the above-mentioned difficulties, we have invented an improved gear shifting system.

In the^^^g^^gear shifting system according to this invention, gearshift to higher gear is
achieved by angular rotation of the twist grip in a predetermine^djrpction,_and...after-...one
gearshift takes place, the twist grip returns back to original position. For nexLgearshjftwthc
twist grip is rotated by same angular rotation and after the shifting has taken place, thejwist
grip returns back to the o£igif^poj>jtiojn. The same method also applies for lower gearshift in the opposite direction. Therefore, at any time during running of the vehicle, after the gear is shifted to either higher or lower gear, the twist grip remains in the same angular position.
One of the objectives of the present invention is to provide a^jmg^^ygear shifting system, Ii
which will have a shorter angular movement of the twist grip considering total angular
movement in the prior art.
Yet another objective of the invention is to have the twist grip return to its original position
after each gear shifting and hence the sequential increase or decrease of angular position of
twist grip is avoided.
Yet another objective of the present invention is to have a positive engagement only to the
next higher or lower gear position for safe driving.
Yet another objective of the present invention is to facilitate the driver to easily reach various
other controls located on twist grip which are meant for switching headlamp, direction
indicators, horn, etc.

This invention provides gear shifting system used in
2 or 3 wheeled vehicles having a handle bar steering control and a hand operated gear shift control located on left hand side of the handle bar comprising a gear shift lever, a slider block, sector plate assembly, a pair of pivot pins, bush for sector plate, a pair of pawls, a pair of washer, a pair of circlips, a lock spring, a guide for spring, a torsion spring, a return spring, a means to avoid oil leakage and dust entry such as O ring or oil seal, screw for roller, a lock plate assembly, a shaft, a pin for roller, a roller, a bracket, a gear shift lever pin, a gasket, a plain washer, a neutral indicator switch, a gear shifter housing, a crankcase magneto side, a tension spring, a pin for return spring and a pair of pins for pawl the said shaft passes through a cylindrical portion of said gear shifter housing, and means to avoid oil leakage and dust entry such as 0 ring or oil seal is provided between the cylindrical portion of said gear shifter housing and outer periphery of said shaft, one end of said shaft is welded co axially to lock plate assembly, Baid lock plate assembly comprises a lock plate and a ratched plate, the other end of said shaft is coupled with gear shift lever with said gear shaft pin, a slider block is rotatably assembled to the end of gear shaft lever^ said slider block is engaged in the cavity of step and the gear shifter housing is

assembled to the crankcase magneto side; said sector plate assembly comprises sector plate upper; a distance piece rand « sector plate with integral lug said lock plate assembly has five grooves on its outer diameter corresponding to neutral, first, fsecond, third and fourth gear positions respectively in which a roller rests and is held in position with a lock spring, said roller is riveted to one end of the bracket with a rivet and the other end of the bracket is provided with a screw which is fitted to said gear shifter housing; said ratchet plate of lock plate assembly is provided with two sets of grooves on its inner diameter corresponding to said four gear positions in which said two pawls are located and are held in position by a tension spring with their profiles in the visinity of said pawls; said two pivot pins and a bush are press fitted on sector plate assembly which is assembled on the said shaft and positioned below the said lock plate assembly, said pawls are free to rotate about the pivot pins and are held in position by washers and circlips, two pins are fixed on the gear shifter bousing and are located in two slots as shown are provided on sector plate assembly so as to actuate the pawls; the said lug of sector plate sub-assembly engages with the legs of the return spring which ie anchored by a pin which is press fitted to gear shifter housing; a guide for spring is assembled on to the said gear shifter housing so that it can guide the return spring which is freely positioned on the the outer periphery of said guide for

spring, the said torsion spring and the said return spring enabling the twist grip to return to the original position after the selection of desired gear position by the rider.
The gear shifting system of the present invention! comprises an outside gear cable and an inside gear cable, a pulley, a bracket for gear cables, a twist grip, a handle bar, a torsion spring, a means to avoid friction such as needle bearing or bush, a spring guide, a bracket for spring, a gear control tube, and a clutch lever, said gear control tube being press fitted to said twist grip and assembled on left hand side of said handle bar and supported on said needle bearing or bush, said pulley being fixed to the gear control tube, said clutch lever being assembled to said twist grip enabling actuation of clutch; said pulley being provided with two holes which allows said outside gear cable and inside gear cable being assembled through said bracket, the other end of said outside gear cable and said inside gear cable being assembled to sector plate assembly, said torsion spring being provided on said spring guide and the lugs of the said spring being anchored to said bracket; the said guide being press fitted to said handle bar.

In the abovementioned shifting system, the said
gear shifting system comprises 3 first gear, a second gear, a third gear and a fourth gear, a main shaft, a stem, a guide bush,

a cross, a crankcase magneto side and a crankcase clutchf said four gears are rotatably assembled on said main shaft so that the axial movement of said gear is restricted on one side by a collar integrally formed on the said main shaft and on the other side by a circlip and a washer, said guide bush acts as a spacer to connect cross and stem; the said cross is threaded on stem and is freely movable awially within said main shaft, said crankcase clutch side, and crankcase magneto side houses the transmission part which is suitable to accommodate the main shaft assembly and the gear shaft housing is assembled to the said crank case magneto side.
According to the present invention the gear shifting system of the 2 or 2 wheeled vehicle is provided with a handle bar steering control and a hand operated gear shift control located on left hand side of the handle bar wherein the said lock plate assembly has three grooves on its outer diamter and said ratchet plate of lock plate assembly is provided with two sets of grooves on it© inner diameter corresponding to two gear positions corresponding to neutral, first and second gear positions respectively or said lock plate assembly has four grooves on its outer diamter and said ratchet plate of lock plate assembly is provided with two sets of grooves on its inner diamter corresponding to three gear positions corresponding to neutral, first, second and third gear positions respectively or said lock plate assembly has si>;

Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings, wherein:
Figure 1 - Illustrates view of vehicle from rear where engine and transmission are located
substantially on one side of the centerline of the vehicle. Figure 2 - Illustrates typical assembly of twist grip on handle bar in the prior art. Figure 3 & 3A - Illustrates typical gear shifting system according to the prior art. Figure 4 - Illustrates typical assembly of speed gears on the main shaft in the prior art. Figures 5A, 5B and 5C - Illustrates typical assembly of twist grip on handle bar of the gear

according to this invention. Figures 7A, 7B and 7C - Illustrates partial views of the gear shifting system according to this
invention in various sections. Figures 8A, 8B and 8C - Illustrates partial view of details and section of the gear shifting
system according to this invention. Figure 9 - Illustrates exploded view of the components of gear shifting system according to
this invention The following description refers to a two-wheeled vehicle wherein the engine (EN) and transmission (TR) unit is positioned substantially on right hand side of longitudinal median plane of the vehicle as shown in Fig 1.
The improved gear shifting system as per this invention essentially comprises of handle bar (78), a twist grip (77), means to avoid friction such as needle bearing or bush (80). a gear control tube (83), a clutch lever (84), a pulley (75), a bracket for gear cables (76), a torsion spring (79), a guide for spring (81), a bracket for spring (82), a gear shifter housing (53), a gear shift lever (21), a slider block (22), a shaft (41), a gear shift lever pin (46), a means to avoid oil leakage and dust entry such as O ring or oil seal (36), a return spring (35), a guide for spring (34), a lock spring (33), a sector plate upper (32), a distance piece (31), a sector plate lower (30) with integral lug (30a), two pivot pin (24 and 24a), a bush for sector plate (25), a pair of pawls (26 and 26a) having profile (P), two washers (27), two circlips (28), tension spring (54), a lock plate (38b), a ratchet plate (38a), a roller (44), a screw for roller (37), a pin for roller (43), a bracket (45), a pin for return spring (51), two pins for pawl (52 and 52a), a neutral indicator switch (49), a gasket (47), a plain washer (48), a outside gear cable (55) and inside gear cable (56), a 15t speed gear (57), a 2nd speed gear (58), a 3rd speed gear (59), a 4th speed gear (60), a main shaft (61), a stem (62), a guide bush (63), a cross (67), a crankcase magneto side (65) & crankcase clutch side (66).

Figure 1 illustrates a two-wheeled vehicle wherein engine and transmission unit (EN and TR) is positioned substantially on the right hand side of the longitudinal median plane of the vehicle when seen from rear of the vehicle.
Figure 2 shows the assembly of handle bar with twist grip as per the prior art and Figure 3 and Figure 3A show two illustrations of the gear-shifting device assembled in housing (H). With reference to above figures, when a gear shifting is desired by a driver, he rotates the twist grip (16) located on handlebar by left hand in clockwise direction when viewed from left hand side of vehicle after pressing clutch lever (not shown), which creates tension force in control cable C2. The other end of control cable C2 is connected to a gear control disc (1) and as the twist grip (16) is rotated, the gear control disc (1) also rotates. Similarly, when the twist grip (16) is rotated in counterclockwise direction when viewed from left hand side of vehicle, which creates tension force in control cable CI. The other end of control cable CI is connected to a gear control disc (1) and as the twist grip (16) is rotated by predetermined angle the gear control disc (1) also rotates. A lever (2) is fixed at predetermined position with respect to said gear control disc (1) with the help of pin Pi and this causes slider block (3) to move, which is riveted (4) to the lever (2). The slider block (3) thus moves along with the lever (2) with reference to axis (Al) of the gear control disc.
The gear control disc (1) has five notches on its outer periphery. A spring (5) and spring loaded lever (6) keeps the gear control disc (1) in position with the help of a roller (7) in one of the notches. The notches Nl, N2, N3, N4 and N5 are the positions of gear control disc (1) corresponding to First, Neutral, Second, Third and Fourth gear engagement position, respectively.
Figure 4 illustrates the assembly of main shaft (14), 1st speed gear (13), 2nd speed gear (12). 3rd speed gear (11) & 4th speed gear (10). The slider block (3) as shown in Fig 2 is engaged in the cavity (8) formed in gear shifter Pin (9), which moves forward and backward along with retainer pin (9B) at the time of gear shifting as the gear control disc (1) rotates about the axis (Al). A cross (9 A) fixed at the end of said pin (9) with the help of threading acts as a key and transmits the rotary motion of one of the gears 13, 12, 11, or 10 depending upon the position of gear control disc (1), to the main shaft (14), which moves the vehicle with the help of rear wheel (not shown) mounted on the main shaft (14). With reference to Fig 2, the positions Nl. N3, N4, and N5 of gear control disc (1) correspond to engagement of gears 13, 12, 11 and 10 respectively. The cross (9A) is maintained at its position with the help of spring (5), bracket (6) and roller (7). In addition, there are various known methods for retaining the gear position.

Figures - 5A, 5B, 5C to 9 illustrate complete gear shifter assembly according to' this invention in various views.
With reference to Figures 5A, 5B and 5C, in the improved gear shifting system according to the invention, one end of gear control tube (83) is provided with hand grip (not identified) and intermediate portion is press fitted to the twist grip (77) which is;assembled on left-hand side of the handle bar (78) of the vehicle and supported on means to reduce friction such as needle bearings or bush (80). A. pulley (75) is fixed to the other end of the gear control tube (83); said pulley (75) has two holes wherein one end each of outside gear cable (55) and inside gear cable (56) are assembled through the bracket (76). The other end of the outside gear cable (55) and inside gear cable (56) are assembled to sector plate assembly (23). A torsion spring (79) with a bracket (82) to anchor the legs of the said spring (79) is provided on a guide (81) which is assembled in the said handle bar (78), enables the twist grip (77) to return to the original position in conjunction with return spring (35) described later, after selection of gear.
With reference to Figures 6A, 6B and 6C, the said sector plate sub-assembly (23) comprises of pre-assembly of sector plate lower (30) with circular slots (SI and S2), distance piece (31) with slots (SI and S2) as shown and sector plate upper (32) with slots (SI and S2) as shown, all the three parts welded in position so as to have the said slots aligned; pivot pins (24) and bush (25) are press fitted on sector plate assembly (23) at respective positions, pawls (26 and 26a) are assembled to and are free to rotate about pivot pins (24 and 24a) and are held in position by washers (27) and circlips (28) and profile (P) is in the vicinity of the pins (52 and 52a). The sector plate assembly (23) is assembled centrally on shaft (41) so that the slots (SI and S2) as shown are aligned with two pins (52 and 52a). Said pins are fixed in the gear shifter housing (53) and are freely located in the circular slots (SI and S2). The sector plate lower (30) also has an integral lug (30a), which engages with the legs of return spring (35). The legs of said return spring (35) are anchored by pin (51), which is press fitted to gear shifter housing (53). Inner diameter of the said return spring (35) is located on outer periphery of the guide (34) which is located on outer periphery of the cylindrical portion of the gear shifter housing (53) and is positioned below the sector plate assembly (23).
A shaft (41) passes through a cylindrical portion of the said gear shifter housing (53). A means to avoid oil leakage and dust entry such as O ring or oil seal (36) is provided between
the cylindrical portion of the said gear shifter housing (53) and outer periphery of the said

shaft (41). One end of the said shaft (41) is welded co-axially to pre-welded sub-assembly of lock plate (38b) and ratchet plate (38a) which is illustrated as lock plate complete (38). The other end of the shaft (41) is assembled with gear shift lever (21) with the help of gear shift lever pin (46). To the end of gear shift lever (21) a slider block (22) is rotatably assembled. The slider block (22) is engaged in the cavity of stem (62) as in case of prior art. Gear shift lever (21) has projection to operate neutral indicator switch (49).
The said lock plate (38b) and ratchet plate (38a) has a set of grooves on outer diameter (N3, A3, B3, C3 and D3) corresponding respectively to neutral, first, second, third and fourth gear positions) in which the roller (44) rests and is held in position against compression load of lock spring (33). The roller is riveted to one end of the bracket (45) with the help of rivet (43) and the other end of the bracket is pivoted with the help of screw (37) which is screwed to gear shifter housing (53). One end of the said lock spring (33) rests in the gear shifter housing (53) and the other end is located on outer periphery of the projection formed on bracket (45)
Two pawls (26 and 26a) are rotatably assembled on pins (24 and 24a) and are held in position with the help of washer (27) and circlips (28). The ratchet plate (38a) also has two sets of grooves on its inner diameter (set no 1 as Nl, Al, Bl, CI and Dl and set no 2 as N2, A2, B2, C2 and D2 corresponding respectively to neutral, first, second, third and fourth gear positions) in which one end of said two pawls (26 and 26a) are located and the other ends are pulled by tension spring (54).
With reference to Figure 7, main shaft assembly consists of a main shaft (61) on which said 1st speed gear (57), 2nd speed gear (58), 3rd speed gear (59), 4th speed gear (60), are rotatably assembled. Axial movement of the said gears is restricted on one side by a collar integrally formed on the said main shaft (61) and on the other side by a circlip with washer (not identified). As illustrated in Figure 7, the gar shifter housing (53) is assembled to crankcase magneto side (65) with the help of studs and nuts (not illustrated).
The guide bush (63) acts as a spacer to connect cross (67) and stem (62), said cross (67) is threaded on stem (62) and these parts are free to move axially in the said main shaft (61) bore when pushed or pulled by the said slider block (22) to select desired gear position. Crankcase clutch side (66) & crankcase magneto side (65) houses the transmission parts which is suitable to accommodate the main shaft assembly and the gear shift housing (53).
The brief description of functioning of the system is as follows.

For N-l-2-3-4 shift (shifting to higher gears for increasing the speed).
The lock plate complete (38) is illustrated in figure 6C when the system is in neutral gear position and sector plate assembly (23) is at the reset (home) position. With reference to Figs 5A and 5B, when a gear shifting is desired by rider, he twists the twist grip (77) fitted on the Left hand side of the handle bar (78) after depressing-the clutch lever (84) in anti-clockwise direction as viewed from Left hand side of vehicle, which rotates said pulley (75) and in turn pulls inside gear cable (56) which causes sector plate assembly (23) to rotate in clockwise direction when viewed from top in figure" 6C. As the twist grip (77) is rotated, it rotates the ' sector plate assembly (23) and pivot pin (24), which causes the pawl (26) to piish ratchet plate (38a) through groove Nl after overcoming the predetermined free play. During this, the pawl (26a) is withdrawn out of action i.e. comes out of groove N2 with the help of the pin (52a) and profile (P) of the pawl (26a). The said lock plate complete (38) will cause the roller (44) to lift from the N3 (Neutral) groove & move towards the A3 (1st gear) groove.
If rider tries to rotate the twist grip (77) further after the roller (44) gets into the A3 (lsl gear) groove, without allowing the sector plate assembly (23) to return to its original position, then ends of the slots (SI and S2) hit the pins (52 and 52a) and hence prevent shifting directly from N3 (Neutral) groove to B3 (2nd gear) groove. This feature permits only consecutive shifting of gears.
The lock plate complete (38) which is coupled to the gearshift lever (21) by the gear shift lever pin (46) causes the slider block (22) & ultimately the cross (67) to move axially to engage in the 1st gear (57) with the main shaft (61). The cross (67) acts as a key and transmits the rotary motion of the 1st gear (57) to the main shaft (61), which moves the vehicle in first gear with the help of rear wheel (not shown) mounted on the main shaft (61).
After getting into the A3 (1st gear) groove, the compression spring (33) retains the lock plate complete (38) in position meant for first gear, whereas the sector plate assembly (23) and twist grip (77) return back to the reset (home) position with the help of spring return (35) and torsion spring (79).
The same sequence takes place while shifting the gears from first to second, second to third and third to fourth gear and at each time the sector plate assembly (23) and twist grip (77) return back to the reset (home) position with the help of spring return (35) and torsion spring (79).

Since the clutch lever will be always in the home position, it is necessary to convey the status
of neutral gear position to the rider. For this purpose neutral indicator switch (49) is actuated
and signal is conveyed to the indicator (not shown) located on the control panel.
For 4-3-2-1-N shift. (Shifting to lower gears for decreasing the speed).
With reference to Figs 5A and 5B, when gear shifting to a lower gear (4th gear to 3rd etc) is
desired by rider, he twists the twist grip (77) fitted on the Left hand side of the handle bar
(78) after depressing the clutch lever (84) in clockwise direction as viewed from Left hand
side of vehicle which rotates said pulley (75) and in turn pulls outside gear cable (55) which
causes sector plate assembly (23) to rotate in counter clockwise direction when viewed from
top.
The gear shift system then works on the similar lines as explained above for N-1-2-3-4 shift.
The description mentioned above particularly relates to a 2 wheeled scooter wherein the engine and transmission unit are combined and substantially located on right hand side of the longitudinal median plane of the vehicle. However, the described principle of gear shifting can be applied to 2 wheeled vehicles having gear shift control on left hand side of handle bar and engine and transmission unit substantially located on the longitudinal median plane of the vehicle or substantially located on left hand side of the longitudinal median plane of the vehicle.
The principle of gear shifting explained above can be adopted on any vehicle irrespective of whether the vehicle employs a monocoque chassis or a tubular frame.
The improved gear shifting system described above has four gears. The same system of operation can be used for a system having 2 or more number of gears.
Although the improved gear shifting system has been described in detail in this specification for 2 wheelers, the same can be used in 3 wheelers having handle bar steering control and left hand operated gear shift control where components similar to prior art are used.
Sector plate assembly (23) and lock plate complete (38) used in the improved gear shifting system described above is made of welded sheet metal. These can be manufactured by forging, investment casting, machining or a combination thereof.
In the improved gear shifting system, we have provided a neutral gear indicator, which is activated when the gear is in neutral position and displayed on control panel. Similarly, we

can have addition sensors to sense the various gear positions like 1,2,3 or 4 and the same can be conveyed to the rider through suitable indicators in the control panel.
In the improved gear shifting system described above, the rider twists the twist grip (77) fitted on the left hand side of the handle bar (78) after depressing the clutch lever (84) in anti-clockwise direction as viewed from left hand side of vehicle for shifting to higher gears for increasing the speed and twists the twist grip (77) fitted on the left hand side of the handle bar (78) after depressing the clutch lever (84) in clockwise direction as viewed from left hand side of vehicle for shifting to lower gears for decreasing the speed.
We have have the improved gear shifting system opposite to this, ie. the rider twists the twist grip (77) fitted on the left hand side of the handle bar (78) after depressing the clutch lever (84) in clockwise

direction as viewed from left hand side of vehicle for shifting to higher gears for increasing the speed and twists the twist grip (77) fitted on the left hand side of the handle bar (78) after depressing the clutch lever (84) in anti-clockwise direction as viewed from left hand side of vehicle for shifting to lower gears for decreasing the speed.
The improved gear shifting system of 2 or 3 wheeled vehicles as described herein and as illustrated in the drawings accompanying herewith and having variations and modifications within the scope of the present invention. Such modification and variations are well within the knowledge skilled in the art without deviating from the scope of the invention.